In this era of information and economic globalization, developing critical thinking skills in college students has been set as a primary goal and learning outcome in higher education. Teaching critical thinking, however, is a great challenge to most EFL teachers. This article, therefore, attempts to examine the nature and teachability of critical thinking, analyze and discuss the functions and types of teacher questions as well as Bloom's Taxonomy of Questions. Its primary purpose is to help EFL classroom instructors gain a deep understanding of teacher questions and get to know how to use higher order questioning to enhance EFL students' critical thinking ability.